For what it's worth, here is my opinion. I have TGC 2019 which I paid $20 CAD. I played it for a few weeks and consider it inferior to PG. I think PP nailed it with the RTSM swing. I will pick up 2K21 when it is similarly discounted because there really isn't another option at this time for a computer golf game.
In regards to the look and quality of courses in TGC and now 2k21, the best community courses in PG look way better and are much more realistic looking. In part it is because the CA in PG allows designers to be more creative. For example, in 2K21 you cannot create a custom pano, object or building. In TGC and 2K21 you see the same background (themes), buildings and objects over and over again. Compare that with the clubhouse in Congressional or the custom tee markers and flags in almost every PG community course. Recent releases like Ballyhack, Tehama and Kinloch are in a different league compared to the highest rated courses in 2K21. There is no excuse for not having pot bunkers considering that 2K21 is the 4th version.
What I have also noticed in TGC and the highest rated 2K21 courses is that the designers equate the quantity of objects with quality. A lot of the so called fictional courses I would call fantasy. I remember a course in TGC where there were a couple of animated horses about 5 yards from the tee box and saw this again from the same designer on a You Tube video of one his 2K21 courses. Another course in TGC had a hydro dam a few yards from the tee box or green (can't remember which). Seriously?
The biggest mistake PP made was not coming up with a console version of PG as I suspect the majority of people who play computer golf games do it on a console.